1. Field of the Invention
The present invention relates to a radiation imaging device, specifically, a radiation imaging device that outputs an image signal corresponding to a radiation dose transmitted through an imaging target.
2. Description of the Related Art
In a medical field, a radiation imaging unit that irradiates radiation such as X-rays to a human body and detects an intensity of radiation transmitted through a human body to image an interior of the human body is used. The radiation imaging unit like this is largely divided into a direct type imaging unit and an indirect type imaging unit. In the direct type imaging unit, radiation transmitted through a human body is directly converted to an electrical signal to extract externally, and in the indirect type imaging unit, radiation transmitted through a human body is incident once on a phosphor to be converted into visible light and the visible light is converted to an electrical signal to extract externally.
As a radiation imaging device that is used in a indirect type imaging unit, an X-ray imaging device where, on a substrate, a photoelectric conversion element, a capacitor and a TFT (switching element) are disposed in the same layer structure is proposed (see Japanese Patent Application Laid-Open (JP-A) No. 08-116044, FIG. 20(b)). In the radiation imaging device, for each of pixels, a pair of upper and lower electrodes, a photoelectric conversion portion disposed between the electrodes and containing a photoelectric conversion film constituted of an inorganic photoelectric conversion material such as amorphous silicon, a capacitor for storing electric charges generated by the photoelectric conversion film and a TFT switch that converts the electric charges stored in the capacitor to a voltage signal to output are formed side by side on a substrate, and further thereon, a phosphor made of cesium iodide (CsI) is disposed through a protective film (SiN film).